So when does S4 start?

[Noname Given]

Is it likely a newer production company would make more than 10 episodes a season?

Nope. The number of Eps. and overall budget are decided by Paramount/Skydance.

Some other Streamers like Disney and Amazon Prime do as low a 6 to 8 episodes a season.

 

[Tuskin38]

20 episodes is too long